Abstract
This paper studies a new concept of using GNSS signals coherently
reflected over relatively smooth ocean and ice surfaces from very low
elevation angles (below ~8°) and received by low Earth
orbit (LEO) satellites to retrieve the tropospheric information. This
approach can provide horizontal profiles of tropospheric zenith delay
and total column water vapor (TCWV) with centimeter-level high precision
and spatial resolutions of 10s of km by ~1km, depending
on the elevation angle, with a sampling spacing of
~100m. This approach can potentially be applied to most
sea ice and calm ocean areas and provide tropospheric sensing data,
which can complement and augment existing observation systems. A few
case studies are conducted in this paper using the Spire grazing-angle
GNSS-R data. The retrieved TCWV is compared to ERA5 products and the
Sentinal-3 OLCI measurements and shows promising performances. The
errors associated with the GNSS-R tropospheric measurements are also
discussed.